Suction box



Patented Apr. 11,1950

UNITED STATES PATENT OFFICE SUCTION BOX Carleton L. Clark, New York, N. Y. Application September 21, 1945, Serial No. 017,810

2 Claims.

This invention relates to the extraction of water from a web of paper-making material that is normally carried on a wire of a paper-making machine, such as of the Fourdrinier type. It is common in such machines to use stationary suction boxes over which the wire passesso that during progress of the wire over the fixed suction box, suction existing in the suction box exerts partial atmospheric pressure differential on the web through the wire that carries it. and thus extracts water from the web. An example of a modern and improved suction box is shown in the U. S. A. patent to Evans-No. 2,039,308, pat ented May 5, 1936. This invention has as its object the provision of improvements over that type of suction box, with a view to increasing the rate of water extraction; the speed of the wire across the suction box; the capacity of the apparatus; and the overall efllciency of the apparatus-meanwhile lessening the degree of suction required and lessening the wear on the travelling wire, and a reduction in pump capacity and power load because of vacuum loss through the box and the belt that moves over it.

The Evans patent shows in general a perforated endless belt taking around two spacedapart rolls. This belt has its upper reach in frictional contact with the underside of the wire, so that movement of the wire moves the upper reach of the belt in the same direction and at the same speed. The under side of the upper reach of the belt (that is, on the side thereof opposite the wire) there is a suction box closed by a top plate or cover which also is perforated. As perforations in the belt become progressively in register with perforations in the top plate of the suction box, suction from the box is exerted through the registering perforations to extract or suck water from the paper web through interstices in the travelling wire that supports the web.

By the use of this invention, the velocity of air and the water it carries, passing from the web through the perforations in the belt is significantly increased while using substantially less suction; the areas of surface contact between the wire and belt is materially decreased while still providing enough for frictional contact so that the wire properly impels the belt at the same speed as that of the wire; the area of registering drainage perforations or ports of the belt and the perforations or slots in the top plate of the suction box is maintained constant at all times; and the amount or degree of suction used can be at least halved with equal water removal. Lateral stretch of the belt is minimized by making it of a plurality of endless belt sections or strips forming 400 tons per day of paper or board, from which as much as 50,000 G.- P. M. of water must be extracted, since the solid content of the web, in the modern methods used, is as little as .02% by weight of the total. That is, in the \.'eb as it is applied to the wire, there is 99.98% water and only .02% cellulosic fibers by weight.

With this in mind, the invention, from at least one viewpoint, may be said to comprise slots in the top plate of the suction box running lengthwise of the box; that is, transversely or across the direction of travel of the belt thereover. The belt is made up so that it has a plurality of water drainage ports so designed and dimensioned that the area of such ports aligned with the slots is constant. And the ported area of the belt presents to the wire, contacting surfaces in the form of intersecting or criss-cross edges rather than flat surfaces.

The best embodiment of the invention now known, is shown in the accompanying drawings, but the embodiment has been chosen for illustrative purposes only, since the invention obviously is capable of other embodiments and some of its details of construction can be changed so long as the ambit of the appended claims is adhered to.

In the drawings, Fig. 1 is an isometric view, with parts in section, of a three-box suction box, the ported belt with the rollers around which it takes, and the travelling wire. Fig. 2 shows in partial plan view, the top plate for the suction box. Fig. 3 shows in partial plan view, the belt. Fig. 4 shows a partial sectional view of the belt. Fig. 5 shows an enlarged plan view of a portion of the belt. Fig. 6 shows an isometric viewof a part of two belt sections. Fig. 7 is a diagrammatic or explanatory view showing the relationship between the slots in the suction box plate and the drainage ports of the belt, as the latter move over and along the former.

In Fig. 1, l I represents the usual web-carrying wire of a paper-making machine, such as a Fourdrinier. On the under side of the web, there is contacted with frictional contact, the upper reach of an endless flexible belt I2. The belt takes around rolls I3 and "and the upper reach of the belt moves in frictional contact with an air-tight suction box indicated generally at I, having a top plate II. The suction box can be single, but it usually is made up of multiple suction boxes or compartments II, II and It, provided with separating walls 23 and 2|. Each suction box, or each compartment thereof, is connected by a pipe or conduit, such as 22 and 23, and so on, to a vacuum or suction-producing machine (not shown). Each top plate It is provided with longitudinally extending slots 28 throughout its major portion, but where deckle edges are tobe made on the machine, the deckling portions of the slot, on each side of the slotted portion, are or may be provided with substantially round perforations 21.

The endless belt, made of some flexible material such as rubber, is provided in its main central portions with drainage ports 30, preferably oblong and rectangular in shape, extending lengthwise or longitudinally of the belt, but of a length that is at least as long as the distance between centers of the slots 26 in the suction-box plate It. Each port 33 is surrounded by ridges or crests such as longitudinally (of the belt) extending ridges or knife edges 3| and laterally (of the belt) extending ridge or knife edges 32. These are made to be as near knife-edges as the rubber permits. Each ridge or crest or knife-edge 3| is a vertex formed by the intersection of two bevelled faces 33 and 34, while each knife-edge 32 is a vertex formed by the intersection of two bevelled faces 35 and 36. Eaohflrainage port with its surrounding bevelled faces and ridges, comprises a more or less funnelshapd drainage outlet through the belt, although elongated in cross-section rather than round as is a usual funnel.

The belt i2 is made up of a plurality of longitudinally extending sections or strips 40. In Fig. 5, the dividing line between the strips is shown by a dot-and-dash line. These strips or sections are secured together transversely thereof preferably by means of a wire or rod 4|. When the strips are secured together, the drainage port 30 are complete, for the recessed half of one drainage-port opening is formed in one belt section, and the other half in the other, both of which being in register as well as the shoulders laterally projecting from each strip, when the belt sections are put together. If the belt is to be used in a machine with deckling accessories, as is usually the case, the major portion of a complete belt is made of the belt sections 40 as described, but flanking this portion laterally on each side thereof, is an unapertured or plain deckle section or portion 42. The side of the deckle portions 42 that contact with the rolls i3 and I4 can be provided with a ridge-like extension 43 for engagement with a complementary groove in the rolls, for the purpose of keeping the belt centered in the machine. The deckle portions 42 and these ridges 43 are not shown in Fig. 1.

Fig. 7 shows the relative positions of a drainage port 33 as it progresses across adjacent slots 26, 28' and 26", respectively, in the suction-box plate N. This figure is made up of a plurality of drainage port positions. A, B, C and D. In position A, the drainage port 30 has passed over the slot 28 uiitll the leading edge 50 of the port has just enountered the front edge of the slot 26'. In this position, the trailing edge SI of the port is hilt about to pass from the front edge of the slot 28. The cross-hatched area indicates that part of the slot and that part Of the port that are in register and which comprises those regisboxes.

tering areas of the openings that permit suction from the suction-box to act thereto to extract water from the web on the wire. In position B, the port 33 has moved forwardly and progressed until its leading edge It coincides with the rear edge of the slot 20 while the trailing edge 3| of the port is Just leaving the rear edge of slot 20. The registering open areas in this position involve the slot 26 rather than the slot 26, but the area content of the openings that are in register remains constant. In position C, the port 30 has again moved forwardly until it is free from or has passed beyond the slot 28, but here again the registering portions of the port and the slot 2!, as shown by the cross-hatching, is constant or equal to the corresponding registering areas in positions A and B. This latter fact is also true of position D, wherein the port 33 has again moved forwardly to extend from center line of slot 26' to center line of slot 26". Here one portion of the registering areas is in slot 28, while another portion thereof is in slot 26", but the total of the two cross-hatched areas is the same as that of the one cross-hatched registering area in positions A, B and C. Since it is important to have the registering openings between slot and port constant, it can thus be seen that regardless of the shape of the drainage ports 30, they must be of a minimum length to reach from the center of one slot to the center of the next adjacent slot, as is exemplified in position D of Fig. 7.

As to dimensions: the preferred dimensions are from one crest 32 to another 1% inches while from one crest (ii to another is W, inch. The slots 30 are about 1 inches long by 4 inch wide. The belt is about 1'; inch thick and each section is inch wide.

In operation, the web-carrying wire ll of the paper-forming machine is propelled in a direction toward the right, as shown by the arrows. This impelled movement of the wire also moves the upper reach of the belt I2 in the same direction due to frictional contact between the two. The suction box I5 is so positioned on the under side of the upper reach of the belt I2 that there is a tight enough, although sliding, contact between them that air leakage into the suction box is minimized. Suction is effected in the suction box l5 by means of the pipes 22, 23 and so on, leading to a suction or vacuum pump. Such suction operates to extract water from the web on the wire II as each longitudinally-extending drainage port 30 of the moving belt comes into register with the slots 26 that extend longitudinally on the top plates IS on the suction box or The actual registering areas of the ports of the moving belt and of the slots at any one moment as compared to any other, remain constant due to the design and dimensionin of the coacting types of openings.

The surface of the belt that comes into contact with the wire may be said to resemble somewhat a waflle, although that simile is not exact, for the drainage ports 30 are likely to be more oblong than square and the knife-edges 3| and 32 surrounding the ports are as sharp as they can be made with the materials used. The reason is that there is to be a minimum of surface contact between belt and wire, and yet what contacting surfaces there are, must be sutllciently distributed to assure that the belt travels at the same speed as the wire. Another reason for this intersecting knife-edge or waflie" arrangement I8 is that the water to be extracted from the web must be carried away therefrom by the air acting as a carrier and the greater the velocity of that carrier, the greater the water extracted, so the less obstruction offered to the passage of the air, the better.

The eflective vacuum area is almost 100% of the surface of the belt over the stationary suction box, thus providing greater drainage verticals to the wire with minimum fibre distortion because of the elimination of water and air travel in a direction approaching parallel to the wire.

The advantage of using longitudinal slots lies in the fact that each individual section of the belt having a longitudinal slot at the bottom of this section is under a continuous and constant vacuum due to the position, length, and shape of this slot as it corresponds to the position and slot openings in the box top itself. There never is a time during the travel of the belt that the water and air is not constantly being drained from these individual sections. The use of a fabricated belt permits the use of larger apertures. eliminating the restrictions in the belt itself which, with the present belt, necessitates a very high vacuum in the box to produce a comparatively low vacuum on the wire. In other words, the loss through the belt is eliminated and a much lower vacuum can be carried in the box to produce the same results on the wire surface. This permits the elimination of an equal quantity of water from the paper or board with half the differential pressure required at present. More specifically, at present of mercury vacuum is required in the box to remove a certain quantity of water at a certain machine speed. The belt of this invention makes possible a vacuum reduction to less than half this amount or approximately 7" mercury vacuum with an actual increase of water removal for the same machine speed and same tonnage. The fact that less vacuum is required in the box itself to obtain the desired results, causes a reduction in the pressure applied by the belt to the surface of the box reducing the frictional drag of the belt across the box surface. The actual square inches of area in contact with the surface of the box with the new design belt, is approximately the same as with the present belt.

The belt of this invention produces a much greater drainage area through the wire as the wire rests on crests or ridges on the belt, whereas with the old belt design there are greater areas of flat surface where drainage directly through the wire from the sheet is impossible, necessitating the water traveling laterally toward the small apertures in the belt or toward the grooves in the belt which leads to these apertures.

I claim:

1. Apparatus for extracting water from papermaking webs carried on a wire of a paper-making machine, which comprises a suction box having a top plate with parallel alternate elongated slots and non-slotted areas laterally between the slots each extending longitudinally of the box and transversely of the machine, means for applying suction to the box, an endless flexible belt having a plurality of drainage ports extending therethrough, and rotatable means for supporting the belt with its upper reach in frictional contact with the underside of the web-carrying wire: characterized in that the parallel slots and the non-slotted intervening areas are continuous and extend entirely across the drainage port containing area of the belt from one side of the belt to the other and the belt has one series of parallel continuous linear crests extending longitudinally of the machine and transversely of the slots of the plate and a second series of parallel continuous linear crests extending transversely of the machine and parallel to the slots with each continuous crest of the second series intersecting each continuous crest of the first series, each of said drainage ports being oblong in shape and being framed on two sides by adjacent crests that are parallel to the machine and on two ends by adjacent crests that are transverse to the machine with the ports all aligned in both directions, and the length of the oblong ports such that each is only as long as the width of one slot plus the width of one non-slotted area of the plate and equally is only as long as from the center of one slot to the center of the next adjacent slot, whereby suction acting through one slot of the'plate is confined to sucking water through only those ports momentarily in register therewith yet the area of the ports through which such suction operates is always constant irrespective of the rate of travel of the belt thus maximizin rapid drainage while minimizing fiber-distortion. 2. Apparatus according to claim 1 wherein the endless flexible belt has plain imperforate marginal side portions and the top plate of the suction box is provided beyond the slots with areas of perforations located beneath the plain imperforate marginal portions of the belt to effect a sealing of the belt at the sides thereof.

CARLETON L. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 395,544 Chapin Jan. 1. 1889 1,640,007 Moravec Aug. 23, 1927 1,876,399 Catala et a1. Sept. 6, 1932 1,978,982 Barstow Oct. 30, 1984 2,039,308 Evans May 5, 1986 FOREIGN PATENTS Number Country Date 3,572 Great Britain of 1880 

